|Publication number||US6975065 B2|
|Application number||US 10/109,170|
|Publication date||Dec 13, 2005|
|Filing date||Mar 27, 2002|
|Priority date||Mar 30, 2001|
|Also published as||CN1384696A, EP1246246A2, EP1246246A3, US20020158576|
|Publication number||10109170, 109170, US 6975065 B2, US 6975065B2, US-B2-6975065, US6975065 B2, US6975065B2|
|Inventors||Tsutomu Yamada, Ryuji Nishikawa|
|Original Assignee||Sanyo Electric Co., Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (12), Non-Patent Citations (1), Referenced by (2), Classifications (13), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to a light-emitting device, and more particularly to increasing the effective light emission area.
2. Description of the Related Art
Flat display panels are recently known to use organic electroluminescence (organic EL) elements. Organic EL elements are self emitting displays in which an electrical current is supplied to an organic EL layer, provided between an anode and a cathode, causing the organic EL layer to emit light. Also since a backlight is unnecessary, unlike LCDs, organic EL elements are expected to be the next major type of flat display panel. In particular, in the active matrix type of organic EL display in which a switching element is formed at each pixel, a larger and higher resolution screen is possible since display data can be stored at each respective pixel.
In this sort of organic EL display, the organic EL layer, which is an emissive layer, is usually formed by a vacuum evaporation process using a shadow mask on a circuit substrate.
An active layer 9 of the thin-film transistor 13 forms a pattern of a double-gate structure that passes twice underneath gate electrodes 11 protruding from the gate line 51. A drain of the thin-film transistor 13 is connected to the data line 52 via a drain electrode 16 and a source is connected to a gate 41 of the thin-film transistor 42 via the storage capacitor 70 and a bridge structure. The storage capacitor 70 is formed from an electrode 55 integrated with the active layer 9 and an SC line 54 connected to power Vsc.
As described in the foregoing, the drain of the thin-film transistor 42 is connected to an organic EL element 60. The organic EL element 60 is comprised from an anode (transparent electrode) 61 that is formed at each pixel on a planarization insulating film 17 on the thin-film transistors 13, 42, a cathode (metal electrode) 66 that is formed in common with the pixels on the topmost layer, and an organic layer 65 that is laminated between the anode 61 and the cathode 66. The anode 61 is comprised from a material such as ITO and is connected via the drain electrode 43 d to the thin-film transistor 42. Furthermore, the organic layer 65 is comprised by sequentially laminating from the anode 61, a hole transport layer 62, an organic emissive layer 63, and an electron transport layer 64. Although the organic emissive layer 63 is composed of a different material for the R pixels, the G pixels, and the B pixels, a material containing BeBq2 that includes a Quinacridon derivative is used.
The above-mentioned components of each pixel are all laminated on a substrate 3. Namely, an insulating layer 4 is formed on the substrate 3, and thereon a semiconductor layer 9 is formed as a pattern. Gates 11, 41 are then formed via a gate oxidizing film 12 on the semiconductor 9. An interlayer insulating film 15 is formed on gates 11, 41, and the active layer 9, such as of poly-silicon, is connected to the anode 61 via a contact hole that is formed in the interlayer insulating film 15.
Furthermore, to form the organic EL element 60 on the transparent anode 61 that is formed at each pixel, the organic emissive layer 63 may be evaporated for each of the R pixels, G pixels, and B pixels using a shadow mask 2 having an opening 2 a corresponding to each pixel as shown in
In this configuration, when a selection signal is output to the gate line 51, the thin-film transistor 13 turns on and the storage capacitor 70 is charged in accordance with the voltage value of the data signal that is impressed on the data line 52 at the time. The gate of the thin-film transistor 42 receives a voltage corresponding to the charge stored in the storage capacitor 70. This controls the current that is supplied to the organic EL element from the power line 53 so that the organic EL element emits light at an intensity that corresponds to the supplied current.
However, when the organic emissive layer 63 is formed by vacuum evaporation using the mask 2 provided with openings 2 a corresponding to the pixels as shown in
The object of the present invention is to increase the effective light emission area during light emission at each pixel in a light-emitting device, such as of an organic EL display.
The light-emitting device of the present invention comprises a first electrode, a second electrode, and an emissive layer formed between the first electrode and the second electrode. At least either the first electrode or the second electrode is formed at each pixel and the emissive layer is in common with a plurality of pixels in adjacency in a matrix. When the pixel is a color pixel, the emissive layer is in common with a plurality of pixels of the same color in adjacency. For example, when a pixel is composed from an R pixel, a G pixel, and a B pixel, the emissive layer is in common with adjacent R pixels, G pixels, or B pixels. An organic electroluminescence material, for example, is used for the emissive layer.
Forming the emissive layer in common or integrally with adjacent pixels instead of at each pixel obviates the use of a mask having an opening corresponding to each pixel and eliminates the shadowing effect that develops at the edges of the openings so that the film thickness of the emissive layer can be made uniform. Making a uniform film thickness of the emissive layer results in the flow of a uniform current in the emissive layer, thereby increasing the effective light emission area.
With the first electrode an anode and the second electrode a cathode, for example, at least either the first electrode or the second electrode is formed at each pixel. Therefore, even though the emissive layer is in common with a plurality of pixels in adjacency, the flow of the current is actually in the portion sandwiched by the first electrode and the second electrode so that the light emission can be controlled at each pixel.
Furthermore, the present invention provides a method for manufacturing the light-emitting device. This method includes the steps of (a) forming the first electrode on a substrate, (b) forming the emissive layer on the first electrode using a mask having an opening, and (c) forming the second electrode on the emissive layer. At least either the first electrode or the second electrode is formed at each pixel, and the emissive layer in step (b) is integrally formed with a plurality of pixels in adjacency by the same opening in the mask.
A mask using this manufacturing method has an opening that is in common with a plurality of pixels in adjacency. When the pixel is a color pixel, the opening is in common with a plurality of pixels of the same color in adjacency. When the pixel is composed from an R pixel, a G pixel, and a B pixel, the opening is in common with R pixels, with G pixels, or with B pixels. The emissive layer for the R pixels is formed using a mask having a common opening for the R pixels, the emissive layer for the G pixels is formed using a mask having a common opening for the G pixels, and the emissive layer for the B pixels is formed using a mask having a common opening for the B pixels.
As described in the foregoing, the film thickness of the emissive layer according to the present invention can be made uniform by forming a common emissive layer. As a result, uneven light emission can be suppressed and the effective light emission area can be increased.
The embodiments of the present invention will be described hereinafter with reference to the drawings while taking an organic EL display as an example.
By using the mask 2 for R, for G, and for B and sequentially vapor depositing the organic EL material as shown in
The configuration of each pixel is substantially similar to that shown in
When forming the organic EL element 65 on the anode 61 in the present embodiment, the mask 2 having the stripe-shaped openings 2 a as shown in
For reference, the conventional formed region of the organic emissive layer 63 is shown shaded in
Thus, in the present embodiment, the opening 2 a of the mask 2 has a striped shape and the organic emissive layer 63 is in common with adjacent pixels of the same color so that the edges of the opening 2 a are not on a boundary of adjacent pixels or a boundary of the anode 61. Therefore, in the case where the organic emissive layer 63 is formed by evaporation, the shadowing effect at the edges disappears, and the film thickness of the organic emissive layer 63 can be made uniform along the column.
In the present embodiment, the organic emissive layer 63 is formed also on the thin-film transistors 13, 42 and the storage capacitor 70. However, since the organic emissive layer 63 has a high resistivity, current flows only through the part sandwiched by the anode 61 and the cathode 66 so that light emission occurs only on the anode 61. Namely, light emission occurs at each pixel.
Although the embodiment of the present invention was described in the above, the present invention is not limited thereto and various modifications are possible.
For example, the present embodiment was described for the case where pixels of the same color are linearly arranged along a column. However, the invention can also be applied for the case where pixels of the same color are arranged in a zigzag manner along a column, such as in a delta arrangement.
Furthermore, although the present embodiment was described for the case in which the organic emissive layer 63 is formed by vapor deposition, the organic emissive layer 63 can also be formed in common by an ink jet method in a similar fashion using the mask 2 (which functions as a frame for limiting the region for dripping ink) shown in
Furthermore, when forming multiple printed panels simultaneously on one large substrate, the mask 2 shown in
While there has been described what are at present considered to be preferred embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.
The present embodiment was described for the case in which the organic emissive layer 63 was formed using a mask. However, the hole transport layer 62, the organic emissive layer 63, and the electron transport layer 64 forming the organic layer 65 can also all be formed using the same mask. The present invention is also applicable in this case. Namely, by having the mask for forming the hole transport layer 62 in common with adjacent pixels, the hole transport layer 62 is in common with adjacent pixels of the same color. Then, as described above, by having the mask for forming the emissive layer 63 in common with adjacent pixels, the emissive layer 63 is in common with adjacent pixels of the same color. Furthermore, similarly for the electron transport layer 64, by having the mask for forming the electron transport layer 64 in common with adjacent pixels, the electron transport layer 64 can be made in common with adjacent pixels of the same color. Besides having the hole transport layer 62, the organic emissive layer 63, and the electron transport layer 64 all in common with adjacent pixels of the same color, the hole transport layer 62 and the organic emissive layer 63 can be in common with adjacent pixels of the same color with the electron transport layer 64 formed at each pixel, or the hole transport layer 62 can be formed at each pixel with the organic emissive layer 63 and the electron transport layer 64 in common with adjacent pixels of the same color.
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|U.S. Classification||313/504, 445/24, 313/505, 313/503, 427/66|
|International Classification||H01L27/32, H01L51/56, H05B33/12, H05B33/10, H01L51/50|
|Cooperative Classification||H01L27/3244, H01L51/56|
|Jun 26, 2002||AS||Assignment|
Owner name: SANYO ELECTRIC CO., LTD., JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:YAMADA, TSUTOMU;NISHIKAWA, RYUJI;REEL/FRAME:013037/0621
Effective date: 20020419
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